The present invention relates to a dynamic vibration absorber for absorbing vibration of a structure, and more specifically to a dynamic vibration absorber for absorbing multidirectional vibration.
In general, radar masts or crane posts of vessels, sail posts of sailboats, etc., are low in vibration damping capability. They sometimes whirl violently when they resonate with the exciting force of main engines or propellers, or when they are exposed to the wind. Projecting long from the hull, these structures are so unstable that they cannot easily be damped, especially if they are large-sized.
Dynamic vibration absorbers of a pendulum type are conventionally known as a means of vibration prevention. In these absorbers, a ring-shaped weight is suspended from the top of a tower by means of a plurality of wires. However, the absorbers of this type cannot practically be applied to low-frequency vibrations with a frequency of one hertz or more.
Also generally known are dynamic vibration absorbers of a spring-supported pendulum type, in which vibration of an oscillating structure is absorbed by a spring-mass system having a natural frequency equivalent to the oscillation frequency of the structure.
However, one such prior art dynamic vibration absorber can absorb only vibration in one direction. Therefore, absorption of, for example, whirling vibration additionally requires the use of another dynamic vibration absorber which absorbs vibration in a direction perpendicular to the first direction, thus necessitating a wide installation space. In order to absorb vertical vibration besides the whirling vibration, still another absorber must be used exclusively for the vertical vibration, requiring a further increased setting space.